Not applicable.
1. Field of the Invention
The present invention relates generally to a disk drive having a conductive path between a disk drive base and a cover through a fastener support.
2. Description of the Prior Art
The typical hard disk drive includes a head disk assembly (HDA) and a printed circuit board assembly (PCBA) attached to a disk drive base of the HDA. The head disk assembly includes at least one magnetic disk, a spindle motor for rotating the disk, and a head stack assembly (HSA). The spindle motor includes a spindle motor hub that is rotatably attached to the disk drive base. The hub has an outer hub flange that supports a lowermost one of the disks. Additional disks may be stacked and separated with annular disk spacers that are disposed about the hub. The head stack assembly has an actuator assembly having at least one transducer head, typically several, for reading and writing data to and from the disk. The printed circuit board assembly includes a servo control system in the form of a disk controller for generating servo control signals. The head stack assembly is controllably positioned in response to the generated servo control signals from the disk controller. In so doing, the attached heads are moved relative to tracks disposed upon the disk.
The head stack assembly includes an actuator assembly, at least one head gimbal assembly, and a flex circuit cable assembly. A conventional xe2x80x9crotaryxe2x80x9d or xe2x80x9cswing-typexe2x80x9d actuator assembly typically comprises an actuator body that rotates on a pivot assembly between limited positions, a coil portion that extends from one side of the actuator body to interact with one or more permanent magnets to form a voice coil motor, and one or more actuator arms which that extend from an opposite side of the actuator body. A head gimbal assembly includes a head which is distally attached to each of the actuator arms. The actuator assembly includes the actuator body that has a bore and a pivot bearing cartridge engaged within the bore. The head gimbal assembly and the flex circuit cable assembly are attached to the actuator assembly.
A variety of fasteners, such a metal screws, are disposed about the cover for attachment of the cover with the disk drive base. A plurality of fasteners is disposed about a periphery of the cover and engages the periphery of the disk drive base. Typically, a fastener is engaged to the pivot bearing cartridge through the cover, and another fastener is engaged to the spindle motor also through the cover.
For any number of reasons, it may be desirable to provide a coating, such as E-coating, about the surface of the cover. For example, the coating may be utilized as a corrosion barrier for protecting the cover. Unfortunately, such a coating may give rise to problems associated with contamination within the disk drive. In this regard, during installation of the fasteners to such a coated cover, the fastener may abrasively contact the surface of the coating thereby producing particulates that tend to contaminate the interior of the disk drive.
Another problem that is introduced with the application of such a coating upon the cover is that the coated cover may become electrically insulated from other portions of the disk drive, because the coating tends to be electrically insulative in nature. In the absence of the coating, the cover is typically in direct contact with the disk drive base thereby grounding the cover. On the coated cover, however, a static electric charge may be built up on the surface of the coated cover. Unless removed, this static electric charge creates a high voltage potential between the cover and the other portions of the disk drive that may discharge to any number of the components within the disk drive, such as the transducers. Such a discharge may damage the disk drive components.
Accordingly, there is a need in the art for an improved attachment arrangement of the disk drive base and the cover in comparison to the prior art.
An aspect of the invention can be regarded as a disk drive that includes a disk drive base and a cover including a cover outer surface and a fastener opening disposed through the cover. The disk drive further includes an electrically insulative coating disposed upon the cover outer surface. The disk drive further includes a fastener that includes a fastener head and a fastener shaft. The disk drive further includes a fastener support disposed adjacent to the fastener opening. The fastener support includes a top surface for engaging the fastener head. The fastener support includes a central opening sized and configured to receive the fastener shaft through the central opening for mechanically coupling the cover and the disk drive base. The disk drive further includes a conductive path disposed between the disk drive base and the cover. The conductive path includes the fastener and the fastener support.
According to an embodiment of the present invention, the fastener support takes the form of a washer. The washer includes a bottom surface and the bottom surface is disposed upon the cover. The bottom surface may be attached to the cover with an electrically conductive adhesive. Alternatively, the washer may be soldered or brazed to the cover for example.
According to another embodiment of the present invention, the fastener support takes the form of a swage nut. The swage nut includes a barrel and a flange extending from the barrel. The flange includes a bottom surface disposed opposite the top surface adjacent the cover. Further, the barrel may include a protrusion for engaging the cover within the fastener opening. Where the cover is formed of multiple layers, the conductive path may include the protrusion and the multiple layers.
The cover is formed of cold rolled steel. The cover may be formed of multiple layers of cold rolled steel and the conductive path may include the multiple layers of cold rolled steel. In addition, it is contemplated that there are a variety of fasteners that may be disposed about the cover for attachment of the cover and the disk drive base. In this regard, the fastener may directly engage with the disk drive base. Further, the fastener may be engaged to a pivot bearing cartridge within the disk drive for mechanically coupling the cover and the disk drive base, or the fastener may be engaged to a spindle motor within the disk drive for mechanically coupling the cover and the disk drive base.